Ceramic coatings



United States Patent M 3,348,355 CERAMIC COATINGS Robert E. Jennings, Birmingham, Ala., assignor, b y mesne assignments, to C.M.C. Corporation, Birmingham, Ala, a corporation of Alabama No Drawing. Filed Aug. 25, 1965, Ser. No. 482,629 7 Claims. (Cl. 53-28) Patented Oct. 24, 19 67 understood, however, that the detailed description, while indicating preferred embodiments of the invention is given by way of illustration only since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Conventional forming elements, be they of the onepiece variety or two-piece variety, i.e., a unit which is composed of a former and a forming tube are coated with chromium oxide in accordance with the procedures set forth in US. Patent 2,707,691, May 3, 1955, and

' U.S. Patent 3,006,782, Oct. 31, 1961. Generally, because Paralleling the growth of the use of form, fill and seal equipment has been the successful development of synthetic polymer coated packaging material such as polymer coated cellophanes. One of such polymer-coated packaging materials is sold commercially under the trademark Olin V3 by Olin Mathieson Chemical Corporation. Because of the improved characteristics of these materials, such as their moisture proofness, strength, durability, appearance and flavor protection, their use has grown steadily for making single and double wall bags on the aforesaid or similar equipment. However,

it has been found that while these highly advantageous and desirable characteristics are provided by the use of polymer-coated packaging materials, certain disadvantages are experienced When the polymer-coated materials are used in association with conventional form, fill and seal equipment presently available. Because of the abrasive elfect of these polymer-coated packaging materials on the equipment parts, especially the forming tubes and collars, rechroming and/or rebuilding of the parts have been required at frequent intervals. When these forming elements are not regularly repaired, their replacement becomes necessary, generally at a cost of several hundred dollars for each part. Additionally, it has also been necessary for the industry to incur the expense of maintaining duplicate parts so that machines can continue to operate While a given part is being repaired.

Heretofore, efforts to overcome these disadvantages have been directed to modifying the polymer-coated packaging materials. Although these modifications in the polymer coatings have lengthened, to some extent, the interval between rechroming, they have not substantially eliminated the need for such reprocessing techniques.

It is therefore a principal object of the present invention to overcome the disadvantages of prior art form, fill and seal equipment in packaging products using a polymer-coated packaging material.

It is another object of the instant invention to provide a forming element coated with a ceramic material.

It is a further object of the instant invention to reduce the abrasive effects of polymer-coated packaging materials on forming elements by providing forming elements with a ceramic coating.

It is yet another object of the instant invention to provide a more efficient and economical method of packaging products using form, fill and seal equipment and polymer-coated packaging material by contacting said packaging material with ceramic coated surfaces of said equipment.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be the forming elements, i.e., the former and forming tubes are of thin wall construction, a powdered bond coat is applied to the surface of the forming element and thereafter the element is provided with a chromium oxide coating according to the principles disclosed in the aforementioned patents.

The powdered bond coat can be of any commercially available material such as Metco 404, which is a composition containing approximately equal parts of NiAl and NiAl and commercially known as Nickel Aluminide. The coating has a specific gravity of 6.0, a typical hardness of Rb (approx.), a softening point over 2750 F. Preferably, the forming element is maintained relatively cool during the application of the chrome oxide coating thereto to prevent undue distortion of these thin wall elements. Generally, the chrome oxide coating has a thickness ranging from 0.01 to 0.015 inch, and an average bulk density of about 4.6 grams/cc.

In addition to providing a forming element having a surprisingly and substantially increased Wear surface, the chrome oxide coating also has been found to substantially eliminate the degradation of the polymer-coated packaging material with which it comes into contact. This highly beneficial effect substantially reduces the moisture vapor transmission rate of the packaging material thus substantially increasing protection of the packaged product.

In accordance with another aspect of this invention, the chrome oxide coating, which is generally crystalline in structure and constitutes a rigid integral coating integral with the forming element base member, has a porosity of the order of 4% (2% open). Occasionally a more porous coating is produced and a porosity up to 25% can be tolerated. It has been found that by impregnating the porous chrome oxide coated forming element with a sealant such as a silicone, a continuous supply of lubricating agent is available, thus substantially eliminating the heretofore need of frequent application to conventional metal forming elements of a lubricant as by spraying. This highly advantageous feature reduces substantially maintenance costs, thus providing a more efiicient and economical packaging process.

The coefiicient of friction of various polymer films on polished chrome plated surfaces and chrome oxide surfaces have been determined as tabulated below:

O oxide coating on the surface of the forming element has particular advantage in reducing the coefiicient of friction of various cellophane film material in contact with the forming element surface. Further, the instant invention provides flexibility in the choice of a particular mechanical treatment of the chrome oxide finish to achieve optimum reduction in the coefficient of friction for specific polymer coated cellophanes. K140202, V-140-3 and l40RS-7 are cellophanes coated with polyvinylidene (Saran) and manufactured and marketed respectively under the above trade mark by E. I. du Pont de Nemours & Co., Inc., Olin Mathieson Chemical Corp, and Avisco Film Corp.

An additional advantage of the instant invention is the reduction in the amount of polymer coating removed from the film packaging material. The removal of the polymer coating permits moisture permeation of the material, thus allowing the product to deteriorate or become stale in a shorter period of time. Prior to the instant invention, a worn forming element having a conventional polished chrome coating exhibited a creased wear pattern after relatively short use. It has been established that on film type packaging material the creases cause a cutting effect on the film which has a pronounced effect on the Product quality as represented by the WVTR factor (Water Vapor Transmission Rate-grams/ 100 sq. in./24 hrs. at 100 F. and 90% RH). In a representative illustration of this phenomenon 0.001 300MSAD Type Cellophane exhibited a WVTR value of 1.5 on a creased Surface while on a flat surface the WVTR value was only 0.3. Accordingly, such a film type packaging material when produced on a creased surface can transmit five times the moisture to the product than one produced on a surface absent such creases. The novel coated forming elements of the instant invention are essentially crease free, i.e., are not susceptible to the development thereon through ordinary wear of creases which produce this disadvantageous effect.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention, reference being had to the appended claims.

What is claimed is:

1. A forming element for packaging machines in which a packaging material is brought into frictional engagement with the surface of said forming element, the improvement which comprises said forming element having a chrome oxide surface.

2. A forming element for packaging machines in which packaging material is brought into frictional engagement with the surface of said forming element, the improvement which comprises said forming element having a porous chrome oxide surface.

3. A forming element according to claim 2 wherein the chrome oxide has a porosity of about 425 percent and an average bulk density of about 4.6 grams/cc.

4. In a method of packaging products on a packaging machine provided with a container forming element comprising forming a container from said packaging film material, charging said container with said product and sealing said container, the improvement comprising frictionally engaging said packaging film material with a chrome oxide surface of said forming element to form said container.

5. In a method of packaging products on a packaging machine provided with a container forming element comprising forming a container from said packaging film material, charging said container with said product and sealing said container, the improvement comprising frictionally engaging said packaging film material with a porous chrome oxide surface of said forming element to form said container.

6. In a method of packaging products on a packaging machine provided with a container forming element comprising forming a container from a packaging film material, the improvement comprising frictionally engaging said packaging film material with a porous chrome oxide surface, the porosity of said surface being about 4-25 percent.

7. In a method of packaging products on a packaging machine provided with a containerforming element comprising forming a container from a packaging film material, charging said container with said product and sealing said container, the improvement comprising frictionally engaging said packaging film material with a porous chrome oxide surface of said forming element to form said container and impregnating said porous chrome oxide surface with a lubricant whereby said forming element is continuously lubricated.

No references cited.

GRANVILLE Y. CUSTER, JR., Primary Examiner. 

4. IN A METHOD OF PACKAGING PRODUCTS ON A PACKAGIN MACHINE PROVIDED WITH A CONTAINER FORMING ELEMENT COMPRISING FORMING A CONTAINER FROM SAID PACKAGING FILM MATERIAL, CHARGING SAID CONTAINER WITH SAID PRODUCT AND SEALING SAID CONTAINER, THE IMPROVEMENT COMPRISING FRICTIONALLY ENGAGING SAID PACKAGING FILM MATERIAL WITH A CHROME OXIDE SURFACE OF SAID FORMING ELEMENT TO FORM SAID CONTAINER. 